Apparatus for light control



March 19, 1940. o. RISZDORFER APPARATUS FOR LIGHT CONTROL Filed March 15, 1935 2 Sheets-Sheet 1 Odb'n Riszdorfer INVE'NTOR. I

ATTORNEYS March 19,1940. 0. RISZDORFER 2,194,031

APPARATUS FOR LIGHT CONTROL Filed March 15, 1935 2 Sheets-Sheet 2 FIG. 6.

' Odb'n Riszdorfer INVENTOR.

A TTORNEYS- Patented 19, 1940 unirso STATES PATENT.

fl FFI'CE Application F15, 1935, Serial No. 11,355?! March 15, ices 11 Claims.

This invention relates to photographic cameras and particularly to photo-electric apparatus for facilitating the proper adjustment of the camera. exposure control devices to assure proper exposure for the then existing light conditions. Certain specific embodiments of the invention claimed herein were disclosed in my application Serial No. 693,204, filed October 11, 1933, which in Patent No. 2,078,481, dated April 6,

It is an object of this invention to provide photo-electric apparatus for a camera whereby when one exposure factor is preselected and the other factor adjusted until a predetermined response is obtained in the photo-electric apparatus the camera will be set for proper exposure.

Another object of the invention is the provision or means for correlating the sensitivity of the photographic film being used in a camera with the exposure factors directly taken into account by the photo-electric apparatus.

Dther objects and advantages of the invention will become apparent from the following description when read in connection with the accompanying drawings and its scope will be pointed ou in the appended claims.

In the drawings:

Fig. L is a perspective view, partly in section and partly broken away, showing one form of the invention applied to a camera;

Mg. 2 is a diagrammatic view showing a modifled arrangement for adjusting the exposure control devices of the camera;

Fig. 3 is adiagrammatic front view showing certain parts of the apparatus shown in Fig. 1;

Fig. 4 is a partial view in perspective of a camera equipped with an electric photometer having its light sensitive cell removably positioned behind the camera lens;

Fig, 5 is a perspective view similar to Fig. 4 but with the camera casing and lens removed; and

Fig. 6 is a detail view partly in section showing an arrangement for varying the light falling on the cell in accordance with two adjustable factors.

"Fig. 1 shows a photographic apparatus in the form of a box camera III provided with exposure control apparatus embodying one form of the invention. In the front wall of the camera. I0 is secured by appropriate means a casing H which supports in a known manner the camera objective (not shown) and forms a housing for mechanisms such as a shutter 12 and a diaphragm B for controlling the exposure of photographic sensitive material supported in the camera HI in any usual manner. The shutter mechanism enarm 16 for releasing the shutter, all of which is well known. The diaphragm is which may be of any known type governs the transmission of light through the objective and is adjustable by means of a toothed disc H which meshes with another toothed disc I8 forming the adjusting means for a second diaphragm 59 whereby the mutual posi-' tive connection causes the dlaphragms l3 and I9 to open and close simultaneously. The diaphragm i8 is preferably provided with a lens (not shown) which is the light transmitting equivalent of the camera objective.

in accordance with the invention, a light sensitive electrical device is provided tor indicatin when the exposure control devices, i. e., the shutter and the diaphragm, are properly adjusted for the existing light conditions. This electrical device includes a iight sensitive cell 20, which preferably is of the photo-voltaic type, positioned to receive light transmitted by the auxiliary diaphragm i9 and connected in series with a resistshoe 2! and an electrical measuring instrument The coil of the measuring instrument 22 is arranged in a imown manner in the field of a magnet 23 and is provided with a pointer 2% which cooperates with a fixed mark 25 to indicate a proper setting of the exposure controlling devices l2 and ill. The pointer 24 and the fixed mark 25 may be located in any observable position and are here shown as arranged in the immediate vicinity of the front element 25 of the View finder with which the camera in is equipped.

The magnitude of the resistance 25 included in the cell circuit is adjustable by means of a sliding contact 2'5 carried by a shaft '28 on which is mounted a cam 29 engaging with the shutter speed setting pin H. A suitable knob 58 for rotating the shaft 28 is provided with an index it for indicating the shutter setting. It is thus seen that adjustment of the shutter speed correspondingly adjusts the resistance 2| to vary the reading of the measuring instrument 22 and that adjustment of the opening of the camera diaphragm l3 correspondingly regulates the transmission of light through the auxiliary diaphragm l9 to the cell 20 to vary the reading of the measuring instrument 22. The device is adjusted in such manner that when the pointer 24 concides with the izxed mark 25 the settings of the shutter l2 and the diaphragm l3 will be so related as to provide proper exposure.

Other factors influencing the choice 01 correct ing discs I! and it which permits adjustment of the relation between the discs, as for example, in accordance with the sensitivity of the film be ing used. For this purpose, handles 52 and '53 may be pressed to displace forwardly the disc 88 to remove it from meshing engaging relation with the disc I! thereby permitting any one oi the indicating marks F, N or S, denoting fast, normal and slow film speeds, respectively, to be brought opposite the single mark on the disc ill after which the handles 52 and 53 are released and the two discs returned to meshing engagement.

Fig. 2 shows an arrangement resembling that above described in connection with its. 1, the main difierence being that the light falling on the photo cell is under the joint control of the adjusting movement of the camera lens diaphragm and the adjusting movement of the shutter speed setting device. As shown in this figure, 9. photo cell is provided with a diaphragm having laminations 39, one end of which lamina tions is'connected with a rotatable ring 32 and the other end is connected to a rotatable ring 33 whereby the eifective opening of the diaphragm as determined by the laminations 36 will depend upon the relative positions oi the two rings 32 and 33. By means of this diaphragm, it is possible to take into account two independent factors, and in the arrangement shown the ring 32 is coupled to the adjusting ring 35 of a diaphragm 34 provided in front of the camera lens and the ring 33 is coupled with the adjust 118 disc 38 of the device for setting the speed of the shutter. The photo cell 30 is connected to the coil or a measuring instrument 8i which is provided with a pointer 38 preferably extending into a position to be observed through the camera view finder as was the case in the arrangement described in connection with Fig. i. In the present case when the pointer 38 is brought toa predetermined reading indicated by the mark 38, the diaphragm 34 and the shutter speed setting disc 38 will be properly adjusted for correct exposure.

when using the arrangement shown in Fig. 2 other factors influencing the final setting of the exposure control devices of the camera, such as the sensitizing of the film or the use of various filters overithe camera lens, may be taken into accountby adjusting the mesh of the several geared rings or by making the reference mark as displaceable by some suitable adjusting mechanism with which the reference mark 39 may be moved to other positions such as those indicated at ll and 42. With this arrangement when the camera diaphragm and shutter speed are adjusted to bring the meter pointer 38' to.

some diflerent predetermined reading such as that indicated at u, the final adjustment will have taken into account some other factor influencing the exposure to be given.

In the arrangements above described a separate light regulating device has been employed iii-front of the light sensitive cell as an aid in bringing about proper adjustment of the exposure .icontrol devices. Such separate light control device may be disposed with according to the form of the invention now to be,described.-,

In Figs. 4. and 5 a. camera embodying custom of the invention is shown in which the photo cell is so arranged in the interior of the camera that it may be moved into and out of the path of the light passing through the object lens of the camera. This camera includes a casing 58 provided in its front wall with an object lens 58. A disc 60 is available for adjusting the speed .oi the shutter which may be of any known type having a snapping lever 65 and a suitable arm Sla for winding the shutter mechanism. Within the camera casing 58 is positioned a magnet 663 of an electrical measuring instrument having a coil 65 arranged in its field through which coil the current of a photo cell 62 is adapted to flow. The meter coil 85 is provided with a movable. pointer 69 which is positioned in the window of the camera iiner 63 and cooperates with a fixed marl: $5 for indicating when the output of the cell 52 has been brought to a predetermined value. @ertain of the above mentioned parts are more cleariyshown in Fig. 5 in which the diaphragm B'l and its adjusting arm Gil are shown. The shutter speed control disc to is provided with a contact 60o which slides over a resistance coll 801:! included in series with the measuring instrument coil 65 and with the photo cell 62.

The photo cell 62 is fixed on a shaft iii a bent end ii of which is connected with the shutter snapping lever 6| in such a manner that when this lever is displaced to the left as shown in the drawings, the photo cell 62 is moved to the position 12 shown in broken lines in Fig. 4 in which position it is no longer in intercepting position for the light transmitted by the lens is. The initial movement or the snapping lever 6| moves the cell 62 to one side and when the lever 5i ismoved further, it actuates the shutter snap-= ping mechanism in any well known manner. When the lever Si is returned to its initial position, the cell 62 will also return to its initial position as shown in Figs. 4 and 5.

In the arrangement just described the dia phragm employed in the camera object lens controls the light reaching the cell during the measuring operation so that no special arrangement is necessary as was the case in the arrangements shown in Figs. 1, 2 and 3.

In the arrangement shown in Figs. e and 5 the adjustment oi the shutter speed influences the reading of the electric photometer by adlusting a resistance in its circuit. A corresponding adjustment of the meter reading may be obtained by varying the light falling on the cell in accordance with the adjustment of the shutter speed and one suitable arrangement for doing this is shown in section in Fig. 6 where for the sake of simplicity only such parts have been shown as are designed difl'erently from the parts shown in Figs. 4 and '5. In this arrangement a light sensitive cell II is mounted in a suitable frame it which supports an annular member 14 which serves as a frame or support for a suitable mechanism, adjustment of which regulates the transmission of light to the cell 18. This light adjusting mechanism is here shown as consisting of a plurality of adjustable flaps 15 each of which is supported on a rotatable pivot in much the same manner as have similar devices been employed on search lights. The positions 01 the flaps IS on their pivots are adjusted by means of a member 1'! connecting the free endsot the flap 15. This connecting member 11. is provided with a suitablelug or cam follower II which by mean: u.

oi. a coil spring Ila is held in engagement with a cam ll provided on the shaft of the adjusting knob I for setting the speed of the shutter. Due to this arrangement the flap I5 will at all times occupy positions corresponding to the setting of the shutter speed as determined by the position of the cam 8|. The photo cell 18 and its light regulating mechanism comprising the flaps 15 are mounted on a shaft 84 supported in a suitable bearing 85 and having at its forward,

end an eccentrically extending arm 86 which interlocks with the shutter snapping lever El whereby the cell '18 and its associated light regulating means will be moved out of the path of light transmitted by the camera objective upon actuation of the shutter snapping lever El in the.

In some of the arrangements described, the

reading of the electrical measuring instrument has been influenced by regulating the light falling on the cell and by regulating a resistance in the circuit connecting the cell to the measuring instrument. It is to be understood that the shutter speed adjusting movement may be employed to regulate the light falling on the cell and that the diaphragm adjusting movement may he employed for regulating a resistance in the cell circuit.

In each of the embodiments described, an electrooptical device has teen employed for indicating to the user when the several exposrne control devices are properly correlated for proper exposure' It of course, obvious that either the opening or the shutter speed may he preselected and the other then adjusted to bring about the desired reading to insure proper ex Although for the purpose of illustrating my -luvelation I have described in detail certain spe ciflc instrument, an adjustable diaphragm in front oithe photocell, a positive connection between the diaphragm of the object" lens and the diaphragm' oi the photocell, and an adjustable resistanoein the circuit of the photocell, the control meohanism of the resistance being positively connected with the speed control device of the shutter.

- 2. Ina device for the control of illumination in photographic cameras, in combination a measwing instnnnent, a photo-cell connected to said lnstnmient, an adjustable diaphragm iii front or the photo-cell, a movable pointer being arranged opposite to a fixed mark in the measuring instrument, an object lens and an adjustable diaphragm therefor, a disconnectable positive connection between the diaphragm of the photo-cell and the diaphragm of the object lens and an adjustable resistance in the circuit of the photo-cell.

3. In a device for the control of illumination in photographic cameras in combination an object lens and a shutter therefor, a photo-"cell arrangedv in the ray path of the light passing through the object-lens, an electrical measuring instrument in the circuit of the photo-celh means for deflecting the photo-cell from the light-ray path during the exposure, means for adjusting the speed of the shutter, an adjustable resistance in the circuit of the photo-cell, and a coupling means between said shutter speed adjusting means and the adjustable resistance wherebythe current of the photo-cell is controlled in accordance with the shutter speed setting.

4. In a device for the control, of illumination in photographic cameras, in combination an object lens and a shutter therefor, a photo-cell arranged in the light-ray path or" the object loose? the photographic camera, the said photo-cell lacing rotatable around an axle, means for turning the photo-cell around this axle, means for actuating said shutter, and a positive connection hetween the deflecting device of the photo-cell and the shutter actuating means.

5. In a device for the control of illumination is photographic cameras in combination as o jeotive, a diaphragm for governing the transmission of light through the objective, a shutter for controlling the exposure period, a light sensitive cell adapted to be activated in accordance the luminous iiux transmitted by the objective its diaphragm, an electrical measuring instru :cc-ent connected to the light sensitive cell, means for adjusting the speed of the shutter, an adjustable member for varying the ratio between the luminous flux transmitted by solo. objective mid its diaphragm and the current supplied the measuring instrument, and a coupling means lee tween said shutter speed adjusting means said adjustable member.

o. in a device for the control of illumination in photographic cameras in combination an olojee tive, an electro-cptical system including an elemerit having an operative position in the of the light transmitted icy the objective, means for moving said element from its operative position, a shutter for controlling the exposure period, "means for actuating the shutter, and means jointly controlling the means for moving said element from its operative position and shutter actuating means.

i. In a photographic camera in which an ice governing the transmission of light through the objective, or light sensitive cell connected to the electrical measuring instrument, a shutter for controlling the exposure period in the camera, shutter actuating means and a control member therefor, movable means ccnnecwd to said control member and arranged that in one peelticn light transmitted by theobjectlve falls on said cell and adapted to he moved upon operation oi said control member to a position where no light falls on the cell.

8. A photographic camera including a diaphragm, a shutter and a member movable to actuate the shutter, a light sensitive device in.- cluding a photo cell, movable means adapted to occupy alternatively two positions in which said cell receives and does not receive, respectively, light transmitted by the diaphragm, n c mp s means operative upon movement of said shutter lit a oil actuating member for moving said movable means to the position where the cell does not receive light.

9. Photographic'apparatus including an objective, a diaphragm for governing the transmission of light through the objective and a shutter for controlling the exposure period, a light sensitive r the shutter adjusting means for correspondingly adjusting said resistance.

10. In a photographic camera in which a predetermined reading of a light sensitive device indicates that the camera is set for proper exposure, a shutter, means for adjusting the interval setting of the shutter, a diaphragm, means for adjusting the opening or the diaphragm, alightsensltive cell, indicating means ,Ior giving a;

reading corresponding to the cell current, a de-rf vice adjustable for varying the transmission of light to said cell, and means coupling'said adjustable device for joint control by the shutter adjusting means and the diaphragm adjusting means.

11. In a. photographic camera in which a predetermined reading of a light sensitive'device indicates that the camera is set for proper exposure, two independent members adjustable to alter the exposure setting of the c'amera, a. light sensitive device including an indicating meter connected to a light sensitive cell for giving a reading, means adjustable for governing the transmission of light to said cell, each of said independent adjustable members being" adapted to effect an adjustment 01 said means, whereby the reading of said meter is changed.

iiDtiN mszDoRFER. 

